Method of and means for receiving radiosignals



Nm. u 1924. mmm

' P. l. WOLD mamon' or AND MEANS Fon RECEIVING mIosIGNALs Filed sept. 14. 1920 Peerf M/ a/d: by .AW y

Patented Nov. 1.1, '1924.

rrsr Frs.

PETER I. WOLD, OF EAST ORANGE, NEW JERSEY. ASSIGNOR TO WESTERN ELECTRIC Y' COMPANY, INCORPORATED, OF NEW YO'RK, N. Y., A CORPORATION OF NEW YORK.

METHOD OF AND MEANS FOR RECEIVING RADIOSIGNALS.

Application led September 14, 1920. Serial N o'. 410,147.-

To all whom t may concern.'

Be it known that I, PETER I. WoLD, a citizen of the United States, residing at'East Orange, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements in Methods of and Mea-ns for Receiving Radiosignals, of which the following is a full, clear, concise, and exact description.

This invention relates to a method of and means for receiving high frequency waves and more particularly to multi-stage detection, demodulatio-n or frequency reduction for radio. signal wave reception.

In short wave radio systems, the frequency of the incoming waves is often too high to permit of eflicient amplification. The use of a detecting circuit in which high frequency waves are combined with other frequency waves to reduce the effective frequency of the received waves has been suggested. In this circuit the signaling waves are combined with locally generated oscillations to give a beat note of frequency above the limit of audibility but low enough to be amplified, and, after amplification, are reduced by a similar operation to some audible frequency. In the suggested arrange ments of this type the frequencies of the two sets of locally generated oscillations differ, hence separate local generators are required.

An object of this invention is to pro-vide a system of this class in which a generator producing oscillations of a single frequency is employed to effect detection or demodulation of the si als.

Another object is to effect successive frequency reduction of incoming Waves by means ofi oscillations fromv a single local source.

An additional object is to enable a local source of oscillations to be associated with different points of a receiving circuit while preventing exchange of energy between the different points of the circuit through the connection with the local source.

These objects are accomplished by employing a supply source producing alternating current of a singlefrequency coupled to a receiving circuit at a plurality of points,r

the circuit being provided with detecting, demodulating or combining means at these points and having amplifying means between each two successive detecting or combining means. In this manner the received waves are combined with alternating current from the supply source or locally generated oscillations to produce a beat note above the audible limit but of a frequency which may be efficiently amplified, and after 'being amplified the resulting beat frequency current is combined with the locally generated oscillations one or more times and detected. The 'frequency of the locally generated oscillations Should be so chosen relatively to the frequency of the incoming waves that after the last step of frequency reduction or detection the resulting beat note current will be of audio frequency. Thus, if 79 is the frequency of the incoming waves, the frequency of the locally generated current q should be such that p-m] is within the audible range.

`1 of the usual type employed in radio signaling is connected to ground at 2, and be.-

tween the antenna and the ground connection is placed a suitable ,fnductance 3 which may be variable. An adjustable condenser 48, shown in Fig. l, may also be inserted between the inductance 3 and ground 2 in order that the antenna system may be tuned to any desired frequency, preferably, the frequency p of the incoming waves which are to be received.

Inductively associated with the antenna is a circuit tuned to the frequency of the incoming waves consisting of the inductance 5 and the condenser 6. Connected in shunt to the condenser 6 is a detector of the electron discharge type which comprises the usual heated filament 7, a grid 8 and a plate 9 enclosed in an evacuated container l0. The input circuit of this detector extending from the filament 7 to the grid 8, includes the secondary of a transformer l1. The

output circuit includes the filament 7 and the plate 9 and contains a'source of electrical energy. 12 and the inductance 13. A polarizing battery 49 for 'the grid may be provided in the input circuit. An alternating current generator 14, which is preferably but not necessarily of the electron discharge type, is adapted to supply oscillations of a selected frequency g through the transformers 15 and 11 to the input circuit-of the detector 10. y,

As thus far described in detail the incoming signal Waves incident upon the antenna 1 and the loc-ally generated oscillations supplied by the generator 14 being applied to the grid 8 cause, as is Well known, a variable current of 4beat frequency, p-qzp, hereafter spoken of as the intermediate frequency, to flow Ain the plate circuit of the detector Which'includes -the inductance 13.

While the source of local oscillations `isshown connected to the input circuit of detector 1.0 it may be stated that the primary of the transformer'll could be inductively associated with the inductance 13. Moreover, While a detector of the electron dischargetype is herein shown and described, it is to be understood that any other detector may be used, though a detector of the form shown isv preferred. I

Inductively connected to the inductance 13 is a circuit consisting of the inductance 16 and the condenser 17.

As is well understood and may be readily demonstrated, by means of the general input-voltage an output-current formula for` three element electron dischargev devices, the current in the output circuit of the detector 10 will contain current components of both the frequencies supplied to its input circuit, double these frequencies and their sum and difference frequencies. `Since the latter or difference frequency pis the one which is to be amplified the tuned circuit comprising the inductance 16 and the condenser 17, which, as stated above, is inductively coupled or associated with the inductance 13 included in the output circuit of the detector, will be made selective of this frequency, thereby largely suppressing the higher. frequency components. This tuned circuit forms part of the input circuit'of anjamplifier 18 which includes the filament -19 and the grid V2O. The output or plate current circult of this amplifier includes the filament 19, the plate 21, a source of electric-al supply 22 and a choke coil 23. The choke coil constitutes a high impedance path for the selected frequency current, thus preventing it from flowing through the source 22, but does not materially affect the fiow of unidirectional space current from the source 22,

suppressed by the tune-d circuit 24-25 and the oscillatory currents selected by this latter circ-uit will be supplied to the input circuit of a second amplifier 26. This input circuit. extends from the hot filament 27 to the grid 28 and includes the oscillatory circuit 24-25- The output circuit of amplifier 26 includes the filament 27, the plate 29, the choke coil 31 and a source of electrical energy 30. The source 3 0 supplies platecurrent to the amplifier. and the coil 31 operates to prevent short-circuiting through the source 30 of the high frequency current, While permitting direct current flow in the plate circuit.

The output circuit of the amplifier 26 is connected to the input ci'rcuit of a detector 37, such connection including a condenser 35 and the secondary of a transformer ,36. A

low impedance path for the amplified current is provided by the condenser A35, Whereas positive current from the source 3() is thereby prevented from polarizing the grid 33. Y

The primary Winding of the transformer 36 is connected through the transformer 15 to the source of locally generated oscillations 14; thus the voltage of intermediate frequency p from the output of amplifier 26 and voltage of frequency g from local source 14 are impressed in series upon the grid 33, which, as is Well understood, will cause a variable current of difference frequency p-.-q:p to flow in the output circuit ofthe detector 37. This latter circuit includes the filament 32, a source of electrical energy 39, a signal translating device 40 shunted by the condenser 51 for high frequency current and the plate 33. Obviously p should be Within the audio frequency y rangement shown in Fig. 2 maybe used.

In this showing, the circuit connecting the oscillatlon generator through the transformer's 15 and 36 is pro-vided with any asymmetrically conducting device to permitl ico .other Words that p equals 1-1 energy fiow in one direction but prevent return fiovv, thereby eliminating all possibility of exchange of energy between the coupled portions of the detector circuit.

Any form of asymmetrical conducting device ma be used for this purpose, but, as herein s own, it consists of a three element electron discharge device co-mprising a hot. filament 41, a grld 42 and plate 43 enclosed in an evacuated vessel 44 and provided With a source of supply of heating current 45 for the filament, and a source of electrical energy 46 in the plate circuit.

The filament of each of the electron discharge devices 10, 18, 26 and 37 is maintained in a heated condition-by a separate source of current 47, though a. single source suitably connected to said filaments could be used.

A three-stage frequency reduction or detection arrangementis schematically illustrated in Figure 3. Details of the circuit connections between the detectors and amplifiers, and the heating filament and plate source have been omitted, since they are identical With those disclosed in Figure 1.

t is to be understood that the intercoupling preventer shown in Fig. 2 may be used in the circuits connecting the local source of oscillations to the receiver circuit if found desirable.

In this arrangement the frequency of the incomin signaling Waves is reduced to an amplifia le frequency in the first stage by the detector D, amplified by the amplifiersV A, successively combined with the locally generated oscillations in the last two stages by the detectors D and D, amplified by the amplifier A introduced between the two last-mentioned detectors and impressed across the terminals of the signal translator 40;

It may be stated that as many ferquency reduction or detection stages as desired may be used.

A detailed description of the method of operation of the detectors and amplifiers is thought to be unnecessary in view of the fact that their action is Well understood.

The preceding description has been directed to telegraphy, but it will be evident that by selecting the frequency of the locally generated oscillations so that p-p:o, or in p current components of speech frequency 71' will be available after the final stage of frequency reduction, ldetection or demodulation to ener ize a telephone receiver. In this case, di culty may be experienced in holding p-p constant, as is the case with the ordinary homodyne detection system, but by sending out a control frequency from the transmitter, as is the practice in homodyne systems, this difficulty may be overcome.

v tuted therefor.

The tuning of the selective circuits will be sufHciently broad to take care of the currentl of carrier frequency modulated by a control frequency,-since there Will be but a small percentage difference between it and the sigthis frequency, while retaining their essential properties of transmitting signal modulated carrier Waves and suppressing inipulses of undesirable frequencies.

The essential principle of this invention resides in the utilization o-f a single source. supplying alternating current of one frequency, to effect multi-stage frequency reduction, detection or demodulation. thusl eliminating one or more .oscillators whose frequency would require careful control. As a consequence, the circuit arrangement is simplified, the efficiency of the system is increased and, owing to the fact that but a single adjustment is necessary to regulate the frequency of the locally generated oscillations, the demands upon the time and attention of the operator are considerablj.' reduced.

While in the preceding description, refer- .ence is made to a particular design of devices and circuit, arrangements, it will be evident that efficient operation does not depend upon these details, hence any of the Well-known means which will effect the functions herein set forth may he substi- Such being the case, it is to be understood that the present invention includes all such modifications as fall within the scope of the attached claims.

Although the invention has been .described yas applied to a radio signalling system, ity

will be readily appreciated that the prin- .ciples of the invention are equally well adapted for 4use with a Wire system employing high frequency currents varied in accordance with signals.

What is claimed is:

1. A method of receiving signals which comprises combining incoming waves with locally generated oscillations of a frequency different from that of the incoming Waves, selectively 4transmitting the resultant composite Waves to the substantial exclusion of the locally generated oscillations and combiningr the locally generated oscillations with the selectively transmitted resultant composite waves.

2. A method of receiving signals which comprises combining incoming Waves with Unt locally generated oscillations of a frequency different from that of the incoming Waves, selectively amplifying the resultant composite Waves to the substantial exclusion of the locally generated oscillations and combining the locally generated oscillations with the selectively amplified resultant composite waves. I

3. A4 method of receiving signals which 'comprises combining incoming Waves with locally generated oscillations of a different" frequency than said waves, thereby producing beat frequency Waves, amplifying the beat frequency Waves, attenuating the locally generated oscillations resulting from the combining action and combining the amplified Waves with the unattenuated lo* cally generated oscillations.

4. A method of receiving signals Which comprises producing locally generated oscillations of a single frequency different from that of incoming Waves, combining incoming Waves With va portion of the locally generated oscillations to produce composite Waves and combining the composite vvaves plifying the resulting beat frequency Waves and combining the amplified Waves With other oscillations from the local source.

7. A method of receiving `signals Which` comprises combining incoming Waves With locally generated oscillations of a different frequency from said Waves to produce beat frequency Waves and combining the latter with other locally generated oscillations of the same frequency.

8. A method of receiving signals which comprises supplying locally generated oscillations from a lsingle source to a` receiving circuit at a plurality of points in succession, preventing the exchange of energy between the supply points of the receiving circuit and observing the signal at another point follovving the last point in said series. l

'9. A method of receiving signals which comprises combining incoming waves With locally generated oscillations, deriving from theresultant Waves oscillations of frequency different from that of either of said incoming Waves or locally generated oscillations, and combining said resultant waves with other oscillations of said locally generated oscillation frequency.

10. A receiving system comprising a series receiving circuit, a local source of oscillations of a frequency different from the in.- coming Waves and rmeans to supply oscillations from said source to the receiving circuit at a plurality'of points.

11. A receiving system comprisingaseries receiving circuit,`a local source of oscillations o f a single frequency different from the incoming Waves, and means to supply oscillations from said source to the receiving circuit at a plurality of points.

12. A receiving systemA comprising a local source of oscillations of a single frequency different from incoming Waves, means to combine oscillations from said source With incoming Waves, means to amplify the resultant composite Waves and means to com-A zov bine other oscillations from said source With 14. A- receiving system comprising a local source of oscillations of a single frequency different from incoming Waves, Imeans to kcombine incoming Waves with oscillations afrom said source, and means for combining other oscillations from said source with the resultant composite Waves.

15. A 'receiving system comprising a local source of oscillations of a single frequency different from incoming Waves, means to combine incoming waves With oscillations from said source, means for selectively amplifying the composite Waves resultingfrom the Wave combining steps and means for combining oscillations from said source with the composite Wavesindependently of said amplifying means.

16. A plurality of frequency changing devices, means for impressing thereon incoming Waves the frequency of which is to be changed, a local source of generated oscillations, parallel means to impress oscillations from said source upon each of -said frequency changing devices for changing the frequency of said incoming Waves, and means to observe the Waves of changed frequency.

17. A signal receivingsystem comprising a' series receiving circuit, alocal source of oscillations of a frequency different from incoming signal waves, means to supplyv oscillations from the local source to the receiving circuit at a plurality of `points and( Y between said oscillation supply points.

18. A signal receiving system comprising a plurality of combining 'means connected in series, a single source producing oscilla- 'tions of one frequency, and separate means toy supply oscillations from said source to said plurality of combining means at a plurality of points. f

19.` A signal receiving systemcomprising a plurality of combining means connected in series, a single source producing oscillations of one frequency, means to connect said source to said plurality of combining means at a plurality of points and means to prevent exchange .of energy from one point of connection of thecombining -means to another through said connecting means.

20. A signal receiving system comprising a receiving circuit, a local source of oscillations of a frequency different from 'the incoming Waves, means to supply oscillations from said local source to the receiving circuit at a` plurality of points to thereby detect the resulting signal.

2.1. A plurality of frequency changing devices, means to. impress thereon incoming waves the 'Y frequency of which is to be changed, 'a local source of generated oscillations and parallel means to impress oscillations from said source upon each of said frequency changing devices for successively changing the frequency of said incoming waves. l

22. A plurality of frequency changing devices, means to impress thereon superaudible incoming waves the frequency of im ress oscillations from said source upon eac of said frequency changing devices for successively changing the frequency of said incoming waves to produce audible waves.

23. In a signal' receiving system, a source of received signaling waves, a plurality'of serially connected three-element electron discharge detectors,'a source of oscillations of `received Waves,

single frequency different from that of the individual means to supply oscillations to each detector from said source, and selective means connected between the output circuit of one detector and the input circuit of a succeeding detector i adapted to transmit most efficiently the difference frequency component in the output circuit of the detector to f which it is connected. t

24. A method of receiving radio signals which comprises receiving radio Waves modulated in accordance with audible frequency Waves, combining the received Waves 'with locally generated oscillations to produce resultant waves and combining the said locally generated oscillations With the resultant Waves to reproduce the originall audible frequency waves.

25. A method of receiving -signals which comprises receivinv lincoming Waves and combining therewith in a plurality of sta es oscillations of a given frequency of which the frequency of the incoming Waves is a multiple.

26. A receiving system comprising a plurality of combining means, means to impress incoming Waves thereon, a source of locally generated oscillations of frequency of which the frequency of tlie incoming waves is a multiple, and means to impress said locally generated oscillations upon said plurality of combining means.

`27. A method of receiving radio telephone signals which comprises receiving radio waves modulated in accordance with audio frequency Waves, combining With the energy thereof in a plurality of stages oscillations of a given frequency of which tlie frequency of the incoming radio waves is a multiple and observing the audio frequency Waves resulting from the combining action.

In witness whereof, I hereunto subscribe my name this 9th day of September, A. D., y

" PETERI. WoLD. 

